Marijuana consumption by Colorado high school students has dipped slightly since the state first permitted recreational cannabis use by adults, a new survey showed on Monday, contrary to concerns that legalization would increase pot use by teens. The biannual poll by the Colorado Department of Public Health and Environment also showed the percentage of high school students indulging in marijuana in Colorado was smaller than the national average among teens.

According to the department, 21.2 percent of Colorado high school students surveyed in 2015 had used marijuana during the preceding 30 days, down from 22 percent in 2011, the year before voters statewide approved recreational cannabis use by adults 21 and older. The first state-licensed retail outlets for legalized pot actually opened in 2014. Nationwide, the rate of pot use by teens is slightly higher at 21.7 percent, the study found.

“The survey shows marijuana use has not increased since legalization, with four of five high school students continuing to say they don't use marijuana, even occasionally,” the department said in a statement.